1. Field of the Invention
This invention relates in general to subsea wellhead installations, and in particular to a locking mechanism for locking a wellhead connector to a wellhead.
2. Description of the Prior Art
A typical subsea well has a wellhead body which is supported by a template on the sea floor. The wellhead body is a tubular member having grooves on its exterior surface. For a producing well, casing and tubing will be landed in the wellhead body. A wellhead connector is secured to the top of the wellhead body. The wellhead connector has dogs, each of which have grooves, to extend in and engage the grooves on the wellhead body. An actuator ring, when moved down, cams the dogs inwardly. Rods, secured to the actuator ring, extend upwardly. Hydraulic cylinders are located at the tops of the rods for moving the actuator ring up and down. If the wellhead connector is to be removed, hydraulic connections are made with the cylinders to pull the actuator ring up to remove the wellhead connector.
A disadvantage of this system is that the hydraulic cylinders remain with the wellhead connector, and thus may be located for long periods of time on the sea floor. After long periods of time, the seals of the hydraulic cylinders could deteriorate, preventing them from operating when one wishes to remove the wellhead connector.